This invention relates to addition polymerizable adducts of active hydrogen compounds and isocyanates and to copolymer dispersions and polyurethane products prepared from such adducts.
Polyurethanes constitute a broad class of polymeric materials having a wide range of physical characteristics. The polymers are produced by the reaction of a polyisocyanate with a polyfunctional compound having an active hydrogen in its structure. This active hydrogen compound is generally a liquid or solid capable of being melted at relatively low temperatures. Most commonly, the active hydrogen compound contains hydroxyl groups as the moieties having the active hydrogen and thus are termed polyols, e.g., the polyols of polyesters, polyester amides, or polyethers, or mixtures of two or more such materials. For reasons of commercial availability and cost, the polyols most commonly employed in the preparation of polyurethanes are the polyethers having hydroxyl terminated chains and hydroxyl terminated polyesters.
Although a wide variety of physical and chemical properties are obtainable by the proper selection of a polyisocyanate and the polyol as well as the conditions under which the polyurethane reaction is carried out, the resulting polyurethane often exhibits properties, e.g., load bearing and processability, which are unacceptable for some applications, particularly for foam applications as well as for elastomer and plastic applications.
To improve such properties, it has been the practice of the art to employ graft copolymer dispersions (often called polymer polyols) prepared from vinyl monomers and polyols in the preparation of polyurethanes as shown in U.S. Pat. Nos. 3,383,351; 3,304,273; 3,523,093; 3,652,639 and 3,823,201. In U.S. Pat. No. 3,304,273, a mixture of styrene and a polar monomer are copolymerized while dispersed in a polyol which is essentially free of ethylenic unsaturation. Unfortunately, stable dispersions cannot be prepared by this technique if high proportions of styrene monomer are employed. Subsequently, in order to overcome this problem, it was found desirable to employ polyols which contain a significant amount of ethylenic unsaturation. As shown in U.S. Pat. No. 3,823,201, such unsaturation was advantageously introduced by reacting the polyol with an organic compound having both ethylenic unsaturation and hydroxyl, carboxyl or epoxy moieties which are reactive with the active hydrogen moiety of the polyol. While these more improved graft copolymer dispersions solve many of the problems confronting the polyurethane art, most require the use of high molecular weight polyols as the continuous phase in order to provide a stable dispersion.
Accordingly, it is highly desirable to provide an improved copolymer dispersion wherein less unsaturated moiety is required in order to achieve a stable dispersion of the polymer in polyols.